How can I stop being jealous of skinny people? (women who have kids answer only please!)?

I am 20 years old and I had my 1st baby 5 months ago. I lost 45 pounds out of the 70 pounds I gained by exercising and brestfeeding, however my milk dried up for some odd reason, and I still exercise. Now I take these body cleansing pills to help lose the other 50 pounds I want to lose but I can't get my stomach down worth crap and I have hideous stretch marks that I can't get over.....I put mederma, palmers cocoa er stretch mark cream, and natural shea er on my stomach ever since I got pregnant and they still look hideous! I can't look at my body no more because I feel I look gross and I am so bitter when I see other women who have flat bellies and no stretch marks.! I weigh 170 pounds and I'm 5'3. I just feel horrible...I even bought new clothes and shoes and I still feel bad about myself! I can't get over it and I have moderate self-esteem. I just need help!